Apparatus for froth flotation



Nov. 7, 1967 APPARATUS FOR FROTH FLOTATION Filed Sept. 21, 1964 5 Sheets-Sheet 1 INVENTOR z I Z r BY wglaw ww 0? ATTORNEYS A. ZVEJNIEKS 3,351,199

1967 A. ZVEJNIEKS APPARATUS FOR FROTH FLOTATION Filed Spt. 21, 1964 5 SheetsSheet 2 INVENTOR (IQ/1 4w a ATTORNEYS Nov. 7, 1967 A. ZVEJNIEKS 3,351,199

APPARATUS FOR FROTH FLQTATION Filed Sept. 21, 1964 5 Sheets-Sheet 5 INVENTOR 2% Z 4/ JM% M 1'24 ATTORNEYS United States Patent 3 351 199 APPARATUS FOll FRoTH FLOTATION Andrejs Zvejnieks, Lakeland, Fla, assignor to A. Z. Products, Inc, Eaton Park, Fla., a corporation of Florida Filed Sept. 21, 1964, Ser. No. 397,799 4 Claims. (Cl. 209--170) This invention relates to the art of beneficiation of mineral values by froth flotation, and is particularly concerned with the flotation treatment of those minerals, typified by phosphate ore, which are prone to form secondary slimes. The invention has both apparatus and process aspects.

Many valuable minerals are beneficiated by froth flotation. Thus, sulfide minerals are separated from gangue by using Xanthate collectors; sylvite is separated from halite by use of higher molecular weight amines as collectors; barite is floated with fatty acids; and a two-step flotation process, consisting of a rougher flotation with soap or fatty acids and a cleaner flotation with amine collectors, is employed in concentration of pebble phosphates.

Especially in flotation with cationic collectors, difliculties are often caused by slime particles. These latter absor-b large amounts of cationic collectors, which circumstance results in high consumption of the collector and also impairs the results of the desirable separation. Consequently, a thorough desiliming of the flotation feed, prior to flotation with cationic collectors, is considered necessary. In addition to meticulous desliming, slime depressants such as starches or polysaccharide gums are often used in separations by cationic flotation.

Sliming difliculties are aggravated in the cases of minerals which tend to form secondary slimes. Thus, some de-slimed soft phosphate particles continue to produce slimes even at the gentlest mechanical agitation of the mineral pulp fed to the flotation cells. On the other hand, some agitation or conditioning with the flotation collector is necessary in order to distribute the cationic collector uniformly over the particles which are to be activated. To avoid the problems caused by secondary slirning, the conditioning time conventionally is minimized or even eliminated in case of cationic flotation of soft phosphate ores. Nevertheless, the sub-aeration flotation machines, most widely used in cationic froth flotation of silica from phosphate concentrates, do agitate and hence cause attrition in the slurry of phosphate particles. Consequently, slimes are formed during the flotation process which phenomenon again increases the consumption of the cationic collector and sometimes makes it diflicult to obtain concentrates satisfactorily low in silica content. The presently known pneumatic flotation cells, which theoretically should produce less attrition, have not proved satisfactory and have almost disappeared from flotation equipment market.

The phosphate flotation feed obtained from Florida pebble phosphate deposits usually is a 35 +150 mesh fraction and contains from 15 to 40% BPL (Bone Phosphate of Lime) by weight. In the first or rougher step of the standard two-step flotation process, this feed material is conditioned with caustic soda, tall oil and fuel oil at about 70% solids: The conditioned feed is treated in sub-aeration flotation machines in which the bulk of the phosphate values is removed as the froth product. The froth product is called the rougher concentrate. The underflow or tailing product, rich in silica and relatively poor in phosphate values, conventionally is discarded. Normally, the rougher concentrate is deoiled and subjected to a second flotation step called sand float" or cleaner flotation circuit. In the cleaner flotation step the bulk of the remaining sand is removed as the froth product by the use of a cationic collector, and the final concentrate is obtained as the machine discharge.

The above-mentioned tailing obtained in the rougher flotation step still contains about 5 to 15% BPL by weight. Nevertheless, the BPL values in the rougher tailing are made up of ditficult-to-float phosphate paritcles. Recovery of these BPL values is usually considered uneconomical and the rougher tailing routinely is discarded.

I have now discovered and invented a flotation apparatus by use of which washing, conditioning and flotation of mineral particles can be carried out under conditions which minimize formation of secondary slimes. My apparatus is especially well suited to handle flotation feed materials which tend to form secondary slimes. Application of my apparatus effects more complete and more economical recovery of mineral values. It also enables recovery of valuable minerals from materials which were hitherto discarded as waste materials.

The employment of the apparatus according to the present invention comprises transporting an aqueous slurry of the flotation feed, over a porous plate while the flotation reagent, air and additional water are introduced under positive pressure through said porous plate; removing the froth product from the top of the water layer over said porous plate; and removing the machine discharge product at a point located at the lower end of said porous plate.

In the forthcoming an embodiment of the flotation apparatus according to the invention will be described, with reference to the accompanying drawings, in which FIG. 1 is a diagrammatic sectional side elevational view of a flotation apparatus according to the present invention;

FIG. 2 is a diagrammatic top elevational view of the flotation apparatus; and

FIG. 3 is a sectional elevation through the apparatus taken on the line 3-3 of FIG. 2.

The apparatus will be described with specific reference to beneficiation of BPL values in a rougher tailing obtained in rougher flotation of Florida pebble phosphate flotation feed.

In the drawing, 11 represents a delivery conduit or feed line extending from a conventional phosphate flotation plant (not shown) to a hydrocyclone 12 located above and in discharging relationship with respect to a washbox 13. A water overflow line 14 connects the upper part of cyclone 12 with a launder or trough 15 extending about three sides of wash-box 13.

Wash-box 13 is provided with a porous bottom inlay 16 made of a layer of coarse sand consolidated and cemented in place with a thermosetting epoxy resin. Water distribution channels 17 are cast in the bottom part of the inlay 16, and are connected to a water pipe 18 and a water distribution pipe 19. These latter are for pumping well water through the water pipe 18, water distribution pipe 19, water distribution channels 17 and the bottom inlay 16 of the wash-box.

A slurry of rougher tailings is pumped continuously through line 11 and cyclone 12 into wash-box 13. Excess water from the cyclone 12 overflows through overflow line 14 into a trough 15 surrounding the upper edge of the wash-box 13. By the action of the Water introduced through the bottom inlay 16, the rougher tailings are kept in fluidized state. Any loose slimes are lifted to the upper part of the wash-box 13 and removed by water which overflows the upper edge of wash-box 13 into the sur-,

rounding trough 15. The slimy water from trough 15 is removed through an exit line 20. It passes to a system of slime settling channels, and canif so desiredbe reused after settling out the slimes. From the wash-box 13 the tailing slurry flows into a flotation cell 21 through an opening 22 located in the lower part of the adjacent wall of the wash-box 13.

Flotation cell 21 is a rectangular or trapeziform elongated trough. Its bottom slopes away from the point at whichthe feed'is introduced. A porous inlay 23, made of sand consolidatedand cementedina matrix of a thermosetting epoxy resin, is located in the bottom part of the flotation cell 21. Air channels 24 are embedded in the inlay 23, andare-connected to an air distributionpipe 25 which, in turn, is connected to a compressor 26 driven by a motor 27.

Water-flotation reagentmixture channels 28 also are embedded in the inlay 23, and these are connected by a water-reagent mixture distribution pipe 29 to a water pump 30 driven by a motor 31. The water-reagent mixture distribution pipe 29-is further connected to a reagent line. 32 which in its turn is connected to a reagent pump 33 driven by amotor 34. The reagent pump is connected to reagent tanks 35, 35 by reagent lines 36 and 37. For introduction of plain water, water channels 38 are embedded in the porousinlay 23, and are connected by a water distribution line 39 with a water pump 40, driven by a motor 41.

In its upper part, flotation cell 21 is divided into compartments 42 by partition walls 43. For removal of the froth product, there are located on the top of the flotation cell 21 rotatingpaddles 44 which paddles are driven by a motor 45 connected to the paddles through a drive 46.

As the rougher. tailings-water slurry enters the flotation cell 21, water-flotation reagent mixture, consisting of .a fatty amine acetate collector and kerosene dispersed in water, is pumped continuously through the water-reagent mixture distribution pipe 29 into water-reagent mixture channels 28 and thence is forced through the pores of. porous inlay 23 into flotation cell 21. The water surge through porous inlay 23 keeps the mineral slurry fluidized and promotes movement of the heavier mineral particles down the slope towards the lower exit, end of flotation cell 21. Simultaneously, fatty amine acetate collector-kerosene mixture dispersed in water is adsorbed on the silica particles making them aerophyllic.

A. continuousstream of compressed air is forced by compressor 26 into air. distribution pipe 25* and thence into air channels. 241' from these air channelsthe compressed air surges through the porous inlay 23. The resultingreactivated silica particles attach themselves to the air bubbles ascending toward the surface, and after reaching the. surface, the silica particles are removed by the. overflowing water, or are paddled oif by means of the. rotating paddles 44. Through a trough 47 surrounding'the flotation cell 21, the silica froth. slurry flows by gravity to a collecting tank. 48 and is discarded through a tailing line 49-by pump 50 driven by motor 51. As the mineral particles flow. towards the exitend of the flotation cell 21', more, and more silica is reactivated. or reagentized, is floated to thesurface, and is removed asa silica tailing.

Under the influence of gravity, and aided by the upwardly directed currents the phosphate particles continue. tomove down the sloping bottom of cell 21 over the. porous inlay 23 and a phosphate-water slurry is removed at a point located at. the lower end and at the bottom of the flotation cell 21 through a discharge device 52 (tube, or trough). tov a concentrate collecting tank 53. From the concentrate. collecting tank 53, the phosphate concentrate slurry is pumped by means of a pump 54 driven by a motor 55 through a line56 to a concentrate tank 57.

One methodfor manufacturingthe. porous inlays 161 and 23, including distributing means for water, air and reagent, shown in the wash-box 13 and flotation cell 21, is by forming them in place. This can be done by mixing about 90% by weight of closely fractionated sand or otherv inert granular material, with about by weight of an epoxy resin-curing agent mixture or an unsaturated polyester resin catalyst mixture. Thus, 92% by weight of 20 +40 mesh sand was mixed with 8% by weight of an epoxy resin-curing agent mixture, and a layer of the mixture was compressed in the bottom of the flotation cell 21. For forming of water distribution channels 38, air channels 24 and water-flotation reagent mixture channels 28, A" steel rods were inserted through holes in the wall of the flotation cell before the mixture was set, and the resin-sand mixture was compressed around said rods. The upper surface of the porous inlay 23 was formed from the compacted resin-sand mixture in the form of an evenly sloping slab. The steel rods were removed from the holes before the resin-sand mixture had fully solidified. After curing of the resin-sand mixture, the water-reagent mixture distribution pipe 29, the air distribution pipe 25 and the water distribution pipe 19 were connected to the channels left by the removal. of the steel rods.

It is possible to practice the invention by pre-conditioning the flotation feed with the flotation reagent-prior to its introduction into the trough-andintroducing through the porous plate only the upward currents of air and water.

An important feature of the invention is that air channels in the porous inlay 23 are alternated with water channels and/ or water-reagent mixture channels; also that said channels are placed at an angle in relation to the general direction of movement of the mineral particles which are treatedin the flotation cell 21 or in the wash-box 13.

It is to be understood that, while the foregoing description discloses one embodiment of my invention, it is not to be taken as a limiting one but rather as illustrative only. Many variationsof the apparatus may be made by those skilled in the art Withoutdeparting from the spirit of the invention.

I claim: 7

1. Aflotation apparatus comprising a sloping trough having a sloping inlayed bottom which is porous and contains embedded therein alternating channels for distri bution of water, air andwater-flotation reagent mixture through the surface said inlayed bottom; means for distributing water, air and water-flotation reagent mixture.

under'positive pressure through the surface of said inlayed bottom by way of said embedded channels; means for introducing a water-flotation feed slurry atthe higher end of the sloping trough; means-for removing a froth product from the upper part of said trough; and means for re moving a machine discharge product at a point located at the lower. end and; at the bottom' of said trough said porous. 'b0tt0m= inlay consisting essentially of uniformly sized granular material the particles of which are consolidated and cementedin place with a thermosetting resin.

2. The flotation apparatus of'claim 1, in which the thermosetting-resin is an epoxy. resin.

3.- The flotation apparatus of, claim 1, in which the thermosetting'resin in an unsaturated polyester resin.

4. The flotation apparatus of claim 1, in which the thermosetting resin is a polyurethane resin.

References. (Zited UNITED STATES PATENTS 1,180,089 4/1916- Thompson 209170 X 1,331,238 2/1920 Callow 209170 X 1,418,514 6/1922 Bailey 209-170 X 1,889,078 11/1932 Schiechel 209--170 X 2,753,045 7/ 1956 Hollingsworth 209-470 2,783,884- 3/1957 Schaub 209 2,816,870 12/1957 Lemtz 209l66 X 3,206,178 9/1965 Lamb 261--122 FOREIGN PATENTS 153,289 9/1953 Australia.

HARRY B. THORNTON, PrimaryExaminer.

R. HALPER, Assistant Examiner. 

1. A FLOTATION APPARATUS COMPRISING A SLOPING TROUGH HAVING A SLOPING INLAYED BOTTOM WHICH IS POROUS AND CONTAINS EMBEDDED THEREIN ALTERNATING CHANNELS FOR DISTRIBUTION OF WATER, AIR AND WATER-FLOTATION REAGENT MIXTURE THROUGH THE SURFACE SAID INLAYED BOTTOM; MEANS FOR DISTRIBUTING WATER, AIR AND WATER-FLOATION REAGENT MIXTURE UNDER POSITIVE PRESSURE THROUGH THE SURFACE OF SAID INLAYED BOTTOM BY WAY OF SAID EMBEDDED CHANNELS; MEANS FOR INTRODUCING A WATER-FLOATION FEED SLURRY AT THE HIGHER END OF THE SLOPING TROUGH; MEANS FOR REMOVING A FROTH PRODUCT FROM THE UPPER PART OF SAID TROUGH; AND MEANS FOR REMOVING A MACHINE DISCHARGE PRODUCT AT A POINT LOCATED AT THE LOWER END AND AT THE BOTTOM OF SAID TROUGH SAID POROUS BOTTOM INLAY CONSISTING ESSENTIALLY OF UNIFORMLY SIZED GRANULAR MATERIAL THE PARTICLES OF WHICH ARE CONSOLIDATED AND CEMENTED IN PLACE WITH A THERMOSETTING RESIN. 